The demand for increasing bit rates in optical communication systems requires the generation of shorter optical pulses. In time domain multiplexed optical communications systems, a multiplicity of low bit rate binary optical pulse data streams are interleaved to form a single high bit rate data stream. To avoid overlap between pulses of different data streams, the duty cycle of the pulses on the low bit rate streams must be small. For example, a low bit rate stream may have a bit rate of 10 Gbits/s. This provides a time slot for each pulse of 100 ps. The pulse must be shorter than 100 ps. But if one wishes to interleave 10 such streams into a 100 Gbits/s system, then ten pulses must be fit into a 100 ps slot. Such short pulses cannot typically be obtained by the use of high speed electronics and conventional sources such as electroabsorbtion modulated lasers (EMLs).
Shorter pulses can be obtained by nonlinear optical pulse compressors. Such compressors typically comprise a source of optical pulses, a length of nonlinear optical fiber having positive dispersive properties (positive group velocity dispersion) and a negative dispersion component such as a grating pair or a prism pair. The nonlinearity increases the spectral bandwidth of the pulse which is chirped by the positive dispersion, and the subsequent negative dispersion component compresses the duration of the pulse to a bandwidth limited pulse.
One difficulty with the conventional pulse compressors is that they typically require long lengths of fiber (typically hundreds of meters) to provide the necessary positive dispersion. Intense pulses traveling along such fiber are subject to nonlinear processes such as stimulated Raman scattering which are detrimental to pulse compression. Accordingly, there is a need for an improved optical pulse compressor.